1. Field of the Invention
The present invention relates to an oil pump capable of suppressing an increase in friction and the occurrence of cavitation and pumping loss.
2. Description of the Related Art
Japanese Patent Application Publication No. 2010-96011 is available as an internal gear pump according to the related art. In Japanese Patent Application Publication No. 2010-96011 (reference symbols provided in the description of Japanese Patent Application Publication No. 2010-96011 are used as is), a passage 11 is provided to extend forward in a rotor rotation direction from a terminal end of a discharge port 7, and fluid pressure is introduced through the passage 11 from the discharge port 7 into a pump chamber 10 that has moved to a position where a capacity thereof is minimized.
A force for separating an inner rotor 4 from an outer rotor 3 is generated on an upper side of a part where the pump chamber 10 is confined by the fluid pressure, and a force for pressing teeth of the inner rotor 4 and teeth of the outer rotor 3 against each other is generated in the rotor on an opposite lower side. Thus, a tip clearance of a pump chamber 10 confining portion is reduced so that liquid leakage through the tip clearance is suppressed, and as a result, a reduction in volumetric efficiency is prevented.
A space g generated between a tooth tip of the inner rotor 4 and a tooth bottom of the outer rotor 3 in the position where the capacity of the pump chamber 10 is minimized communicates with the discharge port 7 via a groove 11a, and therefore, to connect the space g to the groove 11a, the groove 11a is provided in a position where the tooth tip of the inner rotor 4 slides against the tooth bottom of the outer rotor 3. Communication between the pump chamber 10 and both an intake port 6 and the discharge port 7 must be blocked temporarily between a discharge end point and an intake start point, and therefore the pump chamber 10 is provided with an escape portion 12 to let out (displace) a part of a starting end of the intake port 6 forward in the rotor rotation direction.